This invention relates to a fuel injection valve mainly used in an engine for vehicle.
FIG. 7 is a sectional side view showing a conventional fuel injection valve disclosed in, for example, the Unexamined Japanese Patent Application Publication No. Hei 9-324722. In FIG. 7, numeral 31 is a body, and numeral 32 is a hollow cylindrical-shaped sleeve welded after a press fit in the top end of the body 31, and in the upper half of the sleeve 32, the bottom of a tubular core 33 made of magnetic materials is welded after a press fit. Numeral 34 is a bobbin, and numeral 35 is a solenoid coil wound on the bobbin 34, and numeral 36 is a shaft-shaped valve, and numeral 37 is an armature.
Further, FIG. 8 is a sectional side view showing a conventional injection valve disclosed in the Japanese Patent No. 2774153. In FIG. 8, numeral 38 is a core, and numeral 39 is an electromagnetic coil, and numeral 40 is a case, and numeral 41 is an armature, and numerals 42 and 43 are valve bodies, and numeral 44 is a valve seat, and numeral 45 is a valve element, and numeral 46 is a sleeve which has a cylinder portion formed in two steps and is a structure in which a stopper is not placed, and the sleeve 46 is formed in double cylinder shape.
In the conventional examples described above, for both the examples, a sectional area of a portion along the core of the sleeve was not controlled and a section thickness of the sleeve was determined in consideration of only the structural strength of the sleeve. Also, the sectional area of the portion along the core of the sleeve is obviously more than or equal to xc2xd of the sectional area of the core.
Further, for both the examples, the sleeve was manufactured by cutting.
The conventional fuel injection valves are constructed as described above and in the example shown in the Unexamined Japanese Patent Application Publication No. Hei 9-324722, the sleeve is formed in a hollow cylindrical shape, so that an axial length of the armature becomes long and the armature weight becomes heavy. Particularly in the case of a fuel injection valve for cylinder injection, the armature operates under high fuel pressure, so that a large electromagnetic attraction force is required and a side area of the armature needs to be increased, but a length of the armature needs to be lengthened in the case that sleeve is a hollow cylindrical shape, so that the armature weight becomes heavier.
An increase in the armature weight reduces a response of a needle valve and it becomes difficult to ensure a wide flow control range necessary to the fuel injection valve for cylinder injection.
Also, an increase in the needle valve weight increases the occurrence of sound caused by a collision between the end surface of the armature and the end surface of the core and between the top end of the needle valve and the valve seat in the case of opening and closing the needle valve, and this adversely affects noise of a car.
Also, in the Japanese Patent No. 2774153, the sleeve 46 with the cylinder portion formed in two steps has not such a problem described above, but a large inner diameter portion of the sleeve 46 is in contact with an outer diameter portion of the valve body 43, so that a magnetic path detours and the energy loss due to an increase in reluctance occurs. Also, in the lower side of FIG. 8 from the large inner diameter portion of the sleeve 46, the case 40 is constructed so as to make contact with the outside of the valve body 42, so that the outer diameter of this portion increases.
Further, since there is no stopper, an air gap which is a gap between the core and the armature cannot be adjusted, and open time and close time of a solenoid valve cannot be properly adjusted. In a conventional method, the amount equivalent to -this air gap is adjusted by a film thickness of surface treatment of the core and the armature, but a thickness setting range of the film thickness is narrow, and the film thickness changes with time due to wear caused by the collision between the core and the armature.
Furthermore, in the needle valve when opening the valve, the inclination becomes large according to squareness of the core end surface, so that a flow passage sectional area between the valve seat and the top end of the needle valve becomes non-uniform, with the result that spray shapes of fuel vary with products.
Also, there was a problem that a sectional area of a portion along a magnetic path of the sleeve in which an eddy current occurs is large and the occurrence of the eddy current is large and the cost increases.
Further, since the sleeve is conventionally manufactured by cutting processing, there was a problem that it is difficult to make the section thickness to 0.5 mm or less in case that deformation in the processing intends to be not caused and the section thickness becomes thick and thus an outer diameter of a product increases.
The invention is implemented to solve such problems, and it is an object of the invention to reduce a weight of a valve by shortening a length of an armature and increase control accuracy and a control range of a fuel flow by an improvement in response and further decrease operating noise.
A fuel injection valve according to aspect 1 of the invention comprises a valve body coupled to a valve holder, a valve seat which is provided in this valve body and has an orifice, a valve element for separably contacting with this valve seat to open or close the orifice, an armature integrally formed with this valve element, and a coil for forming a magnetic circuit by this armature, a core and a yoke, and further step portions are provided in the core and the valve holder and an L-shaped sleeve fitted in these step portions is provided.
In the fuel injection valve according to aspect 2 of the invention, a stopper is provided between the valve holder and the valve body.
In the fuel injection valve according to aspect 3 of the invention, a sectional area of a portion along the core of the sleeve is less than or equal to xc2xd of a sectional area of the core.
In the fuel injection valve according to aspect 4 of the invention, a rib for structural reinforcement is provided in a corner portion of the L shape of the sleeve.
In the fuel injection valve according to aspect 5 of the invention, the sleeve is formed of a non-magnetic material with an electrical resistivity of 70 xcexcxcexa9xc2x7cm or more and a permeability of 20xc3x9710xe2x88x927 h/m or less at 23xc2x0 C.
In the fuel injection valve according to aspect 6 of the invention, the sleeve is manufactured of a plate material by plastic deformation.
In the fuel injection valve according to aspect 7 of the invention, the sleeve is manufactured by metal injection molding.